Art of stabilizing soap



Patented" Mar. 16, 1937 f UNITED STATES ATENT OFFICE v 2,073,923 ART OF s'ranmzme soar Ernest c. Grocker, Belmont, and Lloyd F. nenderson, Reading, Mass assignors to Arthur 1). Little, IncorporatedT Cambr-idge, Mus, acorporation of Massachusetts No Drawing.

12Claim's.

This invention relates to a method of stabiliz- 10 Efforts to overcome these deleterious changes have been made, but have been only casually effective because the conditions causing and tending to promote such changes remained unknown to the art of soap making until our discovery and -1 disclosure'of them, asset forth in our copending application for patent Serial No. 325,381, filed December 11, 1928, of which the present application isa continuation in part. In this copending application we showed that certain multivalent 20 metals, namely, copper and iron, when present in the form of cations in the soap, act catalytically' to induce and promote the oxidation of some of the constituents ofthe soap, whereupon discoloration and rancidity ensue. Such metal 25 cations, which appear to be present, at least in minute quantitiea'in all soaps, may be derived from many som'ces, including the caustic soda,

fats and oils, perfume ingredients, soap making apparatus, containers, and so forth.

7 Dissociation and -ioniration of such copper and ironcompounds to formcations and anions implies a suitable ionizing and dissociating medium such as water; Water, acting as such a medium, a

is always present in sufflcient amount in the. soap 35 mass to allow the formation of copper and iron cations in the presence of the soap'. While the principal deleterious metals, as indicated, are copper and iron in the form of free cations, the

, copper. cations are by far the more active and 40 cause the greater damage.

I apparently negligible catalytic effect, if any.

, As set forth in our copending application above referred to, copper andiron, while almost always present in soap are normally present in minute 45 amounts which are too small to be detected by ordinary analytical methods, and yet are sumcient tocause serious discoloration and rancidity. For example, if a soap of high purity be prepared which exhibits only a slight tendency to become 50' rancid and as much as two parts of an ionized compound of copper per million parts of soap be added thereto, therequickly results a more serious discoloration and rancidity than would ordinarily be encountered under normal condi- 55. tions of carefully controlled soap manufacture.

Other metals have Application November 27, 1933, Serial No. 699,922

The amount 01' iron cations necessary to cause a like degree of rancidity and discoloration is considerably greater than of copper cations,e. 8., between 10 and 50 times. Hence, it is possible in practice to have a soap in which the content of 5 iron cations is too small to be damaging, But so far as we are aware this is never true of copper .cations, which are deleterious in amounts as small as in the order of one part to fifty million parts.

In other words, the proportion is so small that it 19 is almost certain to be present regardless of the origin, prior preparations and treatments to which the'soap stock has been subjected.

Since the quantities of copper and iron cations which aredeleterious to the soap are too minute to be removed by physical means, from the soap mass, it is a question of rendering them harmless in respect of their catalytic activity towardthe I reactions resulting in the oxidation or rancidity 'of the soap. Two general methods of procedure 20 are described in the foregoing application, that is,

by precipitation in the form of extremely insoluble compounds or by reaction to form complex compounds,-.in which form they no longer produce free metal cations and hence become inactive.

The present invention relates to an .improvea ment of the process according to the second method of procedure, as thus defined. To this end, it is an object of this invention to improve the"seoond type of method of treating soap to in'-' 3 hibit and prev rancidity anddiscoloration, by means of a re available reagent or reagents, other than those described in said copending application. Other objects will appear from the disclosure. 85

While a number of reagents have been foun which to some extent stabilize, soap by acting as complex-formers, we have found by extensive study of hundreds of materials, both organic and inorganic, that only avery few are really eflective 40 to stabilize soap against bothcolor and odor changes and to maintain fully such stability over long periods of time. Aside from these very few excellent stabilizers, we have found that other materials which have been considered as stabilizers or rancidity preventers are unsatisfactory in that they are only partially effective, or they may preserve the odor but injure jhe color, or

their efiectiveness is quickly lost on passage of time. have none or these drawbacks; but, in'addition to the reagents mentioned in our copending application above referred to, they constitute'the few.

practical, complete and permanent reagents of the complex-forming type of which we are aware. 55

The complex-formers of this invention The complex forming reagents which we use in accordance with the present invention are. for example, glutamic and aspartic acids and their metallic salts or direct acid addition products.

6 Glutamic and aspartic acids are amphoteric;

they form compounds with relatively strong alkalies or acids. For example, with sodium or potas-. sium hydroxide; sodium or potassium glutamate (or aspartate) will be formed; with hydrochloric 10 or sulfuric acid, glutamic (or aspartic) acid hydrochloride or sulfate will be formed. This latter type of compounds is referred to herein as acid-salts of glutamic (or aspartic) acid., v

In any case, the use of glutamic or aspartic acid 1 or compounds thereof, or mixtures of these, will introduce the radical f where n= l for aspartic acid and its compounds and n=2 for glutamic acid and its compounds.

Thus, sodiumaspartate is represented by naooc-cni-t m coom NH: glutamic acid hydrochloride is represented b nooc-wnm-cH-cdon.

V NH:.HC1

omitting the HCl from the latter formula gives the formula for glutamic acid.-

Our preferred stabilizing reagent may be added at any convenient step in the soap-making process where it may be thoroughly and evenly .in-

corporated into the soap. For example, it may be added to the-neat soap as made in the kettle. in the manufacture of frame soap; in the manufacture of milled soap it may be similarly added, although it is ordinarilybetterto add it to the mixer (which precedes the milling), at which point perfume materials and coloring-agents are also conventionally added. The amount of stabilizing agent added is about 0.03% of the weight of the soap (on a dry basis) this amount may be varied to suit the circumstances and requirements but will fall generally in'the range of 0.01%

to 0.20% of the weight of dry soap. Addition of the stabilizer as a water solution thereof permits more thorough and uniform incorporation throughout the soap, although it is not absolutely necessary to add it in that way. While smaller amounts of stabilizer may be effective, it is preferable to use amounts within the range specified as such amounts, theoretically in excess ofthe quantity necessary to form complexes with the copper and iron present, provide a reserve of complex-forming material against emergencies such as unexpected excesses of deleterious metal cations in the soap, contaminationfrom further handling, wrappers, etc., and other factors. The excess of stabilizer also protects against eflects of any lack of uniformity in the mixing and mill ing operations,--for no matter how thorough these may be, they carr hardly be expected to make a product whose homogeneity is perfect hyde, etc which have hitherto proposed as anti-oxidants or reducing agents. Some of the latter are only temporarily effective while others are objectionable for various reasons-for example, some introduce quite undesirable properties when used with the highest grades of soaps.

The stabilizers of this invention are sharply distinguished from such so-calied anti-oxidants. The latter are generally unsaturated organic compounds which are easily oxidized as compared But after the anti-oxidant .has become saturated.

- or hasotherwise functioned to the extent of its I capacity,-it no longer oflers any protection, and

, may in fact promote oxidation, so that thereafter the material in which it is incorporated quickly becomes discolored and mold. In con-- trast to such action, the stabilizers of this invention operate by eliminating the cause of oxidation and the resulting discoloration and rancidity,-that is, they eliminate the copper and.

iron cations as such by converting them into harmless complexes in which they are no longer present in active or cationic form.

We claim:

1. The art of stabilizing soap exalt Qt rancidity and discoloration induced by copper andiron cations,which act catalytically to promote oxidation of ingredients of the soap, which comprises incorporating in the soap a reagent containing" theradical of the formula -ooccn,).-cn-eootained in the soap to be treated.

2. The art of stabilizing soap against rancidity Land discoloration induced by copper .and iron cations, which act cataiytically to promote oxidation of ingredients of the. soap, which comprises incorporating-in the soap a free acid of the formula nooo-wmn-cn-coon in which n=1 or 2 in suflicient amount comand discoloration induced by copper and iron.

cations, which act catalytically to promoteoxidation of ingredients of the soap, which com prises incorporating in the soapan acid-salt of 1 acompound containing the radical of the formula ooocn,).on-coo- .a v in which n=1 or 2 and It represents an acid in 'suilicient amount completely to react with the.

contained in the soap to a,

cations, which act catalytically to promote oxidation of ingredients of the soap, which comprises incorporating in the soap a solublemetal salt of an acid having the formula in which 3:1. or 2 in suflicientamolmt complete auras-ea 1y to react with the copper and iron cations con tained in the soap to be treated.

5. The art of stabilizing soap against copper and iron cations which act catalytically to promote oxidation of ingredients of the soap, which comprises adding to the soap mass during manufacture a sufficient amount of reagent selected from the group consisting of glutamic' acid, aspartic acid, the acid-salts thereof, and the soluble metal, salts. thereo,,.c ompletely to react with the copper and iron cations contained in the soap to be treated.

6. Soap stabilized against rancidity and discoloration by the presence therein of a suflicient i5 amount of a compound containing the radical of 20 in which n=1 or 2, completely to react with the copper and iron present therein.

I. Soap containing a stabilizing agent comprising a snflicient amount of a compound selected from' the group consisting of .glutamic and aspartic 25 acids, the acid salts thereof and the soluble metal salts thereof, completely to react with the copper and iron present therein.

' 8. That step in the process of making milled soap which consists in adding glutamic acid 30 hydrochloride to the soap mass during the mixing operation preceding the milling, in suflicient amount completely to react with; the copper and iron present therein.

7 copper and iron present therein.

9. Soap stabilized against rancidity and discoloration by the presence therein of a suflicient amount of a free acid of the formula in which n=1 or 2, completely to react with the copper and iron present therein.

10. Soap stabilized against rancidity and discoloration by the presence therein of an acid-salt of a compound containing the radical of the formula in which n=1 or 2, completely to react with the 12. Soap stabilized against rancidity or discoloration by the presence therein of glutamic acid hydrochloride, in an amount sufllcientcompletely to react with the copper and iron present.

ERNEST C. CROCKER. LLOYD F. HENDERSON. 

